In the preparation of the patent application a search was made. The search disclosed a number of interesting inventions. These are discussed in the following paragraphs.
Roger D. Luebke, U.S. Pat. No. 4,538,954, entitled STACKER CRANE HAVING NARROW MAST STRUCTURE, discloses a fork lift device having a suspended mast 7. The mast 7 is suspended from an overhead trolley which rides on rails 6. At the bottom of the mast 7 there is a vertically movable load supporting carriage 10 comprising a horizontally projecting load engaging fork 11. There is no frame having wheels which engage the floor.
Geradus J. Brouwer, U.S. Pat. No. 4,365,921 entitled FORKLIFT VEHICLE discloses two spaced apart frame members joined at the rear by a transverse member. The transverse member also is mounted for the seat of an operator. There is a fork carriage having forks. The fork carriage is moveable forwardly and rearwardly between the two frame members. There are four wheels with two of the wheels at the rear of the frame members and spaced closely together for steering the forklift vehicle. The forks can move vertically on the forklift carriage. There are hydraulic cylinders for rotating the forklift carriage both forwardly and rearwardly.
Hans Heinrich Schmidt, U.S. Pat. No. 4,102,463, entitled TRANSPORTER FOR SLAB CASTING TABLES, discloses a chassis 12 having ground engaging wheels 13 and 14. There is a steering wheel 15 in front of the transporter. There is centrally located vertically sending mast 19. On the upper end of the mast 19 there is an upper table support frame 22.
Henry F. Carroll, U.S. Pat. No. 3,826,393, entitled SELF-PROPELLED UNLOADER, discloses an unloader having, essentially three contact points with the ground or three sets of wheels with the ground. The position of the contact areas is varied by means of hydraulic cylinders for moving the wheels or contact areas with respect to the frame of the unloader. There is a set of forks 42 which can be elevated. Also, with a load the two contact area's or two wheels can be moved so as to provide more stability for the unloader.
Cecil Goodacre, U.S. Pat. No. 3,610,453, entitled INDUSTRIAL TRUCK, teaches of a truck having a body portion with two spaced apart wheels. There is pivotly attached to the body portion two straddle legs. Each of the straddle legs is on the front or extended end of the wheel. There is a mast optively connecting with the front of the straddle legs. There is a load lifting carriage on the mast. There is no position for an operator to sit and to operate the industrial truck and the load lifting carriage.
John R. Newton, U.S. Pat. No. 3,522,896, entitled LIFT TRUCK, discloses a large lift truck having a frame and wheels. The operator's station and the controls are at the rear of the frame. There is a tiltable or moveable set of lift arms 1. Also, there are clamp arms 91. The lift truck can lift large and heavy objects such as a log or a number of logs or a pipe or a number of pieces of pipe and the like.
Benjamin L. Couberly, U.S. Pat. No. 3,497,095, entitled COUNTERBALANCE APPARATUS FOR A LIFT TRUCK, teaches of a lift truck having a frame and four wheels. There is a steering wheel 36 in the central part of the lift truck. On the front end of the lift truck there is a tiltable lift mast 20 operatively connecting with a lift fork 12. It is possible to vary the elevation of the lift mast 20 thereby varying the elevation of the lift fork 12. Also, as lift mast 20 is tiltable the lift fork 12 is rotatable.
Kurt Steinert, U.S. Pat. No. 3,445,019, entitled FORK LIFT TRUCK HAVING A LIFTING DEVICE MOUNTED FOR PIVOTAL MOVEMENT ABOUT A VERTICAL PIVOTAL AXLE, discloses a fork lift truck having a "C" frame with four spaced apart wheels. There is a mast and a mechanism for raising and lowering a set of forks. The fork lift truck is such that the forks can be on the side or the forks can be rotated and at one end. In other words, it is possible for the forks to pick up an object on the side of the truck and elevate the object to be at the end of the truck.
James E. Joyce, U.S. Pat. No. 3,240,372, entitled EXTENSIBLE MOUNTING APPARATUS FOR HOISTS, teaches of a lift truck in a "U" configuration having a main body portion at the base and two spaced apart legs 10. There is a mast 14. On the mast 14 are two fork tines 30. The mast 14 and the fork tines 30 can move along the two spaced apart legs so that the tines can extend beyond the end of the legs 10 or the tines can be retracted so as to be, mainly, between the legs 10. There is a steering wheel and a place for an operator to stand and to operate the fork lift truck.
Glen W. Way, U.S. Pat. No. 2,421,472, entitled ENDLESS TREAD INDUSTRIAL TRUCK, teaches of the crawler tractor having mast member 11 and 12. Forks 31 operatively connect with mast members 11 and 12.
Edward H. Remde, U.S. Pat. No. 1,837,486, entitled INDUSTRIAL TRUCK, teaches of a truck having a frame with wheels. On one end of the frame there is an operator's platform on which an operator can stand and maneuver the truck and lifting apparatus. At the other end of the frame there is a lifting apparatus comprising forks 29. There is a first mast and a second mast. The forks are associated with the second mast. There is an apparatus on the first mast for raising the housing for the second mast.
Albert W. Streeter, U.S. Pat. No. 1,556,262, entitled ELEVATOR AND ELEVATOR TRUCK, comprising a truck having a frame and four spaced apart wheels. At one end of the frame there is a platform 20 of which an operator can stand and maneuver the truck and the lifting apparatus. At the other end of the frame there is a platform 12 which can be moved vertically. There is a winch 15 connecting with platform 12 for moving the platform vertically.
Generally, there is a frame which is heavy so as to provide stability for a load to be lifted. There is a propelling means and a place for an operator to sit or to stand to control the operation of the truck. On one end of the fork lift truck there is a set of forks which can be elevated or lowered for lifting and lowering a load.
In certain instances there are specialized fork lift trucks for one or two specific applications.